The present invention relates to an image display apparatus using a liquid crystal display device, and more particularly to improvements on a backlight unit for radiating light to the liquid crystal display device.
JP-A-2004-272055 discloses a side light type surface light source apparatus having an optical guide plate and an LED light source for radiating light to the optical guide plate, the optical guide plate having an arc-shaped light incidence concave portion in which the LED light source is accommodated. The optical guide plate has a generally trapezoidal shape increasing its width along a direction moving away from the side where the light incidence concave portion is formed, and a light emission plane on the side opposing the light incidence concave portion, and an optical diffusion unit is selectively disposed on the light emission plane. JP-A-2004-272055 discloses also the structure that a prism plane 13 as the optical diffusion unit is formed in a first area 15 of the light emission plane 14 of the optical guide plate and flat planes 18 and 19 are formed in second areas 16 and 17 in order to make different the degrees of transmission and scattering of emission light in each area.